how can i write html code here please?
Discourse supports many ways to format posts. It supports BBcode, Markdown and HTML.
So if you just dump HTML content in the post, Discourse will try to parse it as post formatting.
If you want to share code, you should put it in a code block. Again, Discourse supports many ways to format posts, so you can choose whatever method is easier for you. You can use BBcode
[code] tags, Markdown
``` tags or HTML
You have a lot of flexibility in formatting posts. Just pick any language you want to use! Just make sure to actually use formatting or Discourse will mangle your post.